Abstract: In the manufacture of a superconducting member fine filaments of niobium or vanadium in a bronze matrix are formed by mechanical reduction, e.g. by drawing, and by solid state reaction the filaments are converted to superconducting filaments of a compound of niobium or vanadium with, typically, one or more of the elements aluminium, gallium, indium, silicon, germanium and tin included in the bronze. Phosphorus is included in the bronze but care is taken to ensure that the bronze in contact with the filaments is free of unwanted impurities and in particular has a very low concentration of phosphorus, desirably in the range 0.01 to 0.05 percent by weight.

Abstract: A superconductor of the general formula A.sub.3 B, e.g. Nb.sub.3 Sn, is manufactured by mechanical fabrication of A filaments in a bronze containing B followed by heat treatment to form A.sub.3 B by solid state reaction from B diffusing through the bronze without melting of the bronze. A pure metal for stabilization is mechanically fabricated together with the other components and protected from diffusion thereinto of any of the other components by a barrier layer of A metal. Superconductor formation on the barrier layer of A metal during the heat treatment is avoided or reduced by surface treatment or surface coating which inhibits A.sub.3 reaction between A and B at the barrier.